[unreadable] Breast cancer is the second-leading cause of cancer deaths in women. Over 200,000 new cases of invasive breast cancer are expected in the USA this year alone. It is anticipated that nearly 40,000 women in the USA would die of breast cancer in 2002. Breast self examination and clinical breast examination (palpation) are the most frequently used diagnostic tools for detecting breast abnormalities, and most breast abnormalities are detected with palpation. The overall goal of this project is the development of tools that will improve the classification of breast lesions, particularly in mammographically-dense breasts using elasticity imaging. The basis of the proposed work is our successful real-time implementation of elasticity imaging on a commercially available ultrasound scanner and initial in vivo results on patients with breast disease. Measurements of the bulk elastic properties of in vitro tissues showed that most breast tissues have non-linear stress-strain relationships, but the non-linearity was highest in cancers. We have observed relative non-linearity in mechanical strain among in vivo breast tissue in our preliminary studies. To enhance and extend that work, we propose the following specific aims: 1) significantly improve the quality of strain image sequences through improved motion tracking and error detection and correction; 2) improve the data acquisition and computational capacity and flexibility of the clinical system by porting the application to a new platform (the Siemens Antares); 3) interface a pressure sensor array to the clinical sonography system to provide data acquisition feedback and encode and display the nonlinearity in the stress-strain relationship of tissues; 4) test these methods with simulated data and experiments with phantoms and human subjects; 5) develop tools to teach clinicians the standard measurement techniques for estimating bulk material properties, such as Young's modulus, how to adapt those techniques to scanning the human body. The result of this effort will be a clinically useful tool for examining the mechanical response of human tissues, and a set of training tools to allow the skilled ultrasound clinician to efficiently learn to use these new tools. [unreadable] [unreadable]